HEMODYNAMIC AND HEMATOLOGIC EFFECTS OF ACANTHASTER PLANCI VENOM IN DOGS

This study was designed to examine haemodynamic and haematologic effec ts of the crown-of-thorns starfish venom (Acanthaster planci venom: AP V) in dogs. Severe systemic hypotension, thrombocytopenia and leukopen ia were induced by APV (1.0 mg protein/kg i.v.), followed by gradual r eturn to the baseline level within 60 min. Hypotension was presumably caused by two factors: an early decrease in systemic vascular resistan ce and the large reduction in cardiac output due to reduced ventricula r filling. Indomethacin, a cyclooxygenase inhibitor, remarkably suppre ssed systemic hypotension induced by APV. The peak reduction in system ic pressure was associated with concomitant rise of plasma 6-keto-PGF( 1 alpha), a major stable metabolite of prostacyclin. Thus, the hypoten sive effect of APV may be caused primarily by prostacyclin and/or some vasodilating prostaglandins. In contrast, thrombocytopenia and leukop enia were not affected by cyclooxygenase inhibitor, 5-lipoxygenase inh ibitor or platelet activating factor (PAF) receptor antagonist. When A PV was administered repeatedly, tachyphylaxis was developed in haemody namic effects, but not in haematologic effects. These findings suggest that APV-induced hypotensive effects may occur mainly through endogen ous production of vasodilating prostaglandins including prostacyclin, although APV-induced thrombocytopenia and leukopenia may be caused by other mechanism(s) unrelated to arachidonate metabolites and/or PAF.